Crystal Structure Control
of Zinc-Blende CdSe/CdS Core/Shell Nanocrystals: Synthesis and Structure-Dependent
Optical Properties
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Abstract
Nearly monodisperse zinc-blende CdSe/CdS core/shell nanocrystals
were synthesized by epitaxial growth of 1–6 monolayers of CdS
shell onto presynthesized zinc-blende CdSe core nanocrystals in one
pot. To retain the zinc-blende structure, the reaction temperature
was lowered to the 100–140 °C range by using cadmium diethyldithiocarbamate
as a single-source precursor and primary amine as activation reagents
for the precursor. Although the wurtzite counterparts grown under
the same conditions showed optical properties similar to those reported
in the literature, zinc-blende CdSe/CdS core/shell nanocrystals demonstrated
surprisingly different optical properties, with ensemble single-exponential
photoluminescence decay, significant decrease of photoluminescence
peak width by the shell growth, and comparatively high photoluminescence
quantum yields. The lifetime for the single-exponential ensemble photoluminescence
decay of zinc-blende CdSe/CdS core/shell nanocrystals with 3–4
monolayers of CdS shell was reproducibly found to be approximately
16.5 ± 1.0 ns